Known in the art is an internal combustion engine arranging in the engine exhaust passage an NOX storage catalyst which stores NOX contained in the exhaust gas when the air fuel ratio of the inflowing exhaust gas is lean and releases the stored NOX when the air fuel ratio of the inflowing exhaust gas is a stoichiometric air fuel ratio or rich and arranging a compact three-way catalyst in the engine exhaust passage upstream of this NOX storage catalyst (see for example Japanese Patent Publication (A) No. 2004-108176). In this internal combustion engine, if the NOX storage ability of the NOX storage catalyst approaches saturation, the air fuel ratio of the exhaust gas is temporarily made rich whereby NOX is released from the NOX storage catalyst and reduced.
However, there is a problem in that, in this internal combustion engine, when making the NOX storage catalyst release NOX by feeding mist fuel upstream of the NOX storage catalyst, the NOX released from the NOX storage catalyst cannot be properly reduced.